1. Field of the Invention
This invention relates to an up converter of a base station transmitter of an wireless communication system and more particularly to an up converter of base station transmitter of an wireless communication and method of controlling outputs of the up converter to maintain stabilized outputs, matching the wireless communication system in accordance with improving a structure of the up converter.
2. Description of the Prior Art
An up converter is a communication device for converting a lower frequency signal into a higher frequency signal, and has been used to convert a intermediate frequency modulated from a low frequency into a higher frequency to transmit in a long distance at a video and audio transmitter for a TV broadcasting system or an wireless communication system. Generally, the video signal for TV broadcasting system is converted to VHF or UHF signal and the audio signal is converted into a higher frequency, matching bandwidths of communication manner, i.g. from about 64 Mhz to 1.2 GHz.
FIG. 1 is a block diagram illustrating an up converter of a base station transmitter in mobile communication system based on Code Division Multiple Access Type. The up converter of a base station transmitter shown in FIG. 1 is general type, and has been applied to general base station transmitter.
With reference to FIG. 1, an analog signal output from a baseband processing circuit of a base station transmitter is inputted to an attenuator 11 and attenuated the input signal at predetermined power level. Both an output signal of the attenuator 11 and a single frequency provided from a local oscillator 19, are inputted to a mixer 12 to mix each other. Thus, first of all, frequency of the input signal of the up converter is up converted in the stage.
Subsequently, an output signal of the mixer 12 is inputted to a band pass filter 13 and filtered to pass only a predetermined frequency bandwidth. An output signal of the band pass filter 13 is inputted to an amplifier 14 and amplified with a predetermined amplification ratio. Both an output signal of the amplifier 14 and a single frequency generated from a local oscillator 20 up/down convert an input frequency, are inputted to a mixer 15 to mix each other. Thus, the frequency of the input signal, which is already converted, is up converted in the stage.
Next, an output signal of the mixer 15 is inputted to a band pass filter 16 and filtered to pass only a predetermined frequency bandwidth. An output signal of the band pass filter 16 is inputted to a variable attenuator 17 and adjusted with the output signal level of the band pass filter 16 by the operation of a processor 21. At this event, a adjustment voltage of the variable attenuator 17 is setup in initial stage of applying the up converter to adjust the output signal of the attenuator 17. And an output signal of the variable attenuator 17 is inputted to an amplifier 18 and amplified with a predetermined amplification ratio, and transmitted to outward through a power amplifier and an antenna which are not shown in FIG. 1.
As described above, there was problems that the input signal of the up converter is directly inputted to the first mixer 33 and the output signal of the variable attenuator is directly transmitted to the outward through the second amplifier in the related art of up converter. Accordingly, if the radio signal transmitted form the up converter is not reached completely to a corresponding base station""s area, a managing station of the mobile communication system could not find exact causes that the problem is caused by no applying the input signal to the up converter or working at out of order in the related up converter. The manager of the mobile communication system have to check each state of a lots of base station transmitters including an up converter in order to repair in the circumstance.
Therefore, an object of the present invention is to solve the disadvantage involved in the related art, and to provide an up converter of base station transmitter of an wireless communication and method of controlling outputs of the up converter to control output signals of the up converter in accordance with the strength of the input signal level and output signal level of the up converter.
Also, it is the other object to provide to an up converter of base station transmitter of an wireless communication and method of controlling outputs of the up converter to minimize the variation of output signals of the up converter caused of characteristics and temperature of elements equipped in the up converter or the variation of communication circumstance by improving the structure of the up converter.
In order to achieve the above object, there is provided to an up converter of a base station transmitter in an wireless communication system, the up converter comprises an input level detection section for detecting an input signal of the up converter; a variable attenuator for attenuating converted frequency in the up converter; an output level detection section for detecting an output signal of the up converter; a processor for outputting a control signal to adjust the variable attenuator in accordance with the detected results of the input level detection section and the output level detection section.
In order to achieve the other object, there is provided to an up converter of a base station transmitter in an wireless communication system, the up converter comprises an input level detection section for detecting an input signal of the up converter; a first variable attenuator for attenuating converted frequency in the up converter by a first control voltage; a second variable attenuator for attenuating converted frequency outputted from the first variable attenuator; a processor for providing a second voltage to the second variable attenuator in order to adjust a strength of the output of the first attenuator; an output level detection section for detecting an output signal of the up converter; an automatic gain controller for outputting the first control voltage to adjust the first variable attenuator in accordance with the detected results of the input level detection section and the output level detection section, and the second voltage provided from the processor.